Method of producing core-shell particles and multilayer ceramic electronic component including core-shell particles

ABSTRACT

A method of producing a core-shell particle includes introducing a barium titanate-based base powder and an additive to a reactor, and exposing the barium titanate-based base powder and the additive to a thermal plasma torch to obtain core-shell particles including a core portion having barium titanate (BaTiO3) and a shell portion including the additive and formed on a surface of the core portion.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit under 35 USC 119 (a) of KoreanPatent Application No. 10-2019-0154377 filed on Nov. 27, 2019 in theKorean Intellectual Property Office, the entire disclosures of which areincorporated herein by reference for all purposes.

TECHNICAL FIELD

The present disclosure relates to a method of producing core-shellparticles and a multilayer ceramic electronic component including thecore-shell particles.

BACKGROUND

As the trend for multifunctionalization, lightweightedness andminiaturization of electronic products is rapidly progressing, thenecessity of small and high-performance electronic components isincreasing, and demand for electronic components requiring highreliability, corresponding to electronics and industries such asautomobiles and networks, is also greatly increased.

Accordingly, competition for technological development of passivecomponents such as inductors, capacitors, and resistors to meet marketdemand is accelerating. In detail, multilayer ceramic capacitors are arepresentative field in which technological competition is fierce.

The multilayer ceramic capacitor is largely composed of a dielectriclayer based on BaTiO₃ (BT), an internal electrode based on a metal, andan external electrode containing a metal (Cu) and glass, for capacitanceimplementation. Through developing high-capacitance products based onthinning of dielectric layers and internal electrodes and throughimproving reliability at high temperatures as well as high pressure, andmoisture resistance, in addition to improved microstructures, manyefforts are being made to secure the relevant market.

BaTiO₃ (BT) is one of the most important materials in manufacturing ahigh performance multilayer ceramic capacitor, and it is no exaggerationto say that the ceramic material determines most of the performance.

However, by the simple mixing method or heat treatment, which is therelated art method of producing core-shell particles, since theuniformity of the particles decreases and the designated additivematerial is added by random coating, there is a problem in terms of thedispersion of the material and the distribution of products for thefinished product.

Therefore, there is a need for research into a method of producingparticles having a core-shell structure, capable of uniformly coating BTpowder of a multilayer ceramic capacitor and an additive that determinesthe function thereof.

SUMMARY

This Summary is provided to introduce a selection of concepts insimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

An aspect of the present disclosure is to provide a method of producingcore-shell particles and a multilayer ceramic electronic componentincluding the core-shell particles.

According to an aspect of the present disclosure, a method of producinga core-shell particle includes introducing a barium titanate-based basepowder and an additive to a reactor, and exposing the bariumtitanate-based base powder and the additive to a thermal plasma torch toobtain a core-shell particle including a core portion having bariumtitanate (BaTiO₃) and a shell portion including the additive and formedon a surface of the core portion.

According to an aspect of the present disclosure, a multilayer ceramicelectronic component includes a ceramic body including a dielectriclayer, and internal electrode layers disposed to face each other withthe dielectric layer interposed therebetween in the ceramic body. Thedielectric layer includes a core-shell dielectric grain including a coreportion having barium titanate (BaTiO₃) and a shell portion disposed ona surface of the core portion, and the core-shell dielectric grain is acore-multishell dielectric grain in which the shell portion has multiplelayers.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will be more clearly understood from the following detaileddescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a flowing drawing illustrating a process of producingcore-shell particles of a core-shell structure according to anembodiment;

FIG. 2 is a particle flowing drawing illustrating a process of producingcore-multishell particles of a core-shell structure according to anotherembodiment;

FIG. 3 is a schematic view illustrating core-multishell particles of thecore-shell structure of FIG. 2 ;

FIG. 4 is a perspective view schematically illustrating a multilayerceramic capacitor according to another embodiment; and

FIG. 5 is a cross-sectional view taken along line I-I′ of FIG. 4 .

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. However, various changes,modifications, and equivalents of the methods, apparatuses, and/orsystems described herein will be apparent to one of ordinary skill inthe art. The sequences of operations described herein are merelyexamples, and are not limited to those set forth herein, but may bechanged as will be apparent to one of ordinary skill in the art, withthe exception of operations necessarily occurring in a certain order.Also, descriptions of functions and constructions that would be wellknown to one of ordinary skill in the art may be omitted for increasedclarity and conciseness.

The features described herein may be embodied in different forms, andare not to be construed as being limited to the examples describedherein. Rather, the examples described herein have been provided so thatthis disclosure will be thorough and complete, and will fully convey thescope of the disclosure to one of ordinary skill in the art.

Herein, it is noted that use of the term “may” with respect to anexample or embodiment, e.g., as to what an example or embodiment mayinclude or implement, means that at least one example or embodimentexists in which such a feature is included or implemented while allexamples and embodiments are not limited thereto.

Throughout the specification, when an element, such as a layer, region,or substrate, is described as being “on,” “connected to,” or “coupledto” another element, it may be directly “on,” “connected to,” or“coupled to” the other element, or there may be one or more otherelements intervening therebetween. In contrast, when an element isdescribed as being “directly on,” “directly connected to,” or “directlycoupled to” another element, there may be no other elements interveningtherebetween.

As used herein, the term “and/or” includes any one and any combinationof any two or more of the associated listed items.

Although terms such as “first,” “second,” and “third” may be used hereinto describe various members, components, regions, layers, or sections,these members, components, regions, layers, or sections are not to belimited by these terms. Rather, these terms are only used to distinguishone member, component, region, layer, or section from another member,component, region, layer, or section. Thus, a first member, component,region, layer, or section referred to in examples described herein mayalso be referred to as a second member, component, region, layer, orsection without departing from the teachings of the examples.

Spatially relative terms such as “above,” “upper,” “below,” and “lower”may be used herein for ease of description to describe one element'srelationship to another element as illustrated in the figures. Suchspatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, an element described as being “above” or “upper”relative to another element will then be “below” or “lower” relative tothe other element. Thus, the term “above” encompasses both the above andbelow orientations depending on the spatial orientation of the device.The device may also be oriented in other ways (for example, rotated 90degrees or at other orientations), and the spatially relative terms usedherein are to be interpreted accordingly.

The terminology used herein is for describing various examples only, andis not to be used to limit the disclosure. The articles “a,” “an,” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. The terms “comprises,” “includes,”and “has” specify the presence of stated features, numbers, operations,members, elements, and/or combinations thereof, but do not preclude thepresence or addition of one or more other features, numbers, operations,members, elements, and/or combinations thereof.

Due to manufacturing techniques and/or tolerances, variations of theshapes illustrated in the drawings may occur. Thus, the examplesdescribed herein are not limited to the specific shapes illustrated inthe drawings, but include changes in shape that occur duringmanufacturing.

The features of the examples described herein may be combined in variousways as will be apparent after an understanding of the disclosure ofthis application. Further, although the examples described herein have avariety of configurations, other configurations are possible as will beapparent after an understanding of the disclosure of this application.

The drawings may not be to scale, and the relative size, proportions,and depiction of elements in the drawings may be exaggerated forclarity, illustration, and convenience.

Subsequently, examples are described in further detail with reference tothe accompanying drawings.

FIG. 1 is a flowing drawing illustrating a process of producingcore-shell particles of a core-shell structure according to anembodiment.

Referring to FIG. 1 , a method of producing a core-shell particleincludes introducing a barium titanate-based base powder and an additiveto a reactor, exposing the barium titanate-based base powder and theadditive to a thermal plasma torch, and obtaining core-shell particlesincluding a core portion having barium titanate (BaTiO₃) and a shellportion including the additive. The shell portion is formed on a surfaceof the core portion by exposing the barium titanate-based base powderand the additive to the thermal plasma torch.

Hereinafter, a method of producing core-shell particles according to anembodiment will be described in detail for respective steps.

In the method of producing core-shell particles according to anembodiment, first, introducing the barium titanate-based base powder andthe additive to a reactor 100 is performed.

According to an embodiment, unlike other embodiments to be describedlater, the barium titanate-based base powder and an additive may beintroduced to the reactor 100 in the form of a mixture thereof.

When the mixture of the barium titanate-based base powder and theadditive is added to the reactor 100, the mixture may be introduced tothe reactor 100 through one feeder 110.

Next, exposing the barium titanate-based base powder and the additive tothe thermal plasma torch 120 is performed.

By exposing the barium titanate-based base powder and the additive tothe thermal plasma torch 120, only the barium titanate-based base powdersurface is activated in a rapid heating and cooling manner (>10⁶ K/s).In addition, velocity of the particles is 100˜2,000 m/s.

The surface-activated barium titanate-based base powder and theadditives present in the surroundings react with each other to formcore-shell particles.

For example, according to an embodiment, the barium titanate-basedpowder and the additive are exposed to the thermal plasma torch 120 toobtain core-shell particles 3 including a core portion 1 includingbarium titanate (BaTiO₃) and a shell portion 2 including the additiveand formed on the surface of the core portions 1.

In this case, the grain growth of the barium titanate-based base powdermay be suppressed to maintain the uniformity of the particles, and thereaction time is relatively short to perform mass production andcontinuous production.

For example, according to an embodiment, core-shell particles forobtaining high performance and high reliability multilayer ceramiccapacitors may be implemented by applying thermal plasma synthesis.

The thermal plasma torch 120 has a thermal plasma supply unit in acentral portion thereof, and has a structure in which a torch isdisposed around the center, and the structure thereof is notparticularly limited thereto.

FIG. 2 is a particle flowing drawing illustrating a process of producingcore-multishell particles of a core-shell structure according to anotherembodiment.

FIG. 3 is a schematic view schematically illustrating core-multishellparticles of the core-shell structure of FIG. 2.

A method of producing the core-shell particle 3 according to anotherembodiment includes introducing a barium titanate-based base powder 1 tothe reactor 100 through a first feeder 110 a and introducing a firstadditive 2 a to the reactor 100 through a second feeder 110 b, exposingthe barium titanate-based base powder 1 and the first additive 2 a to afirst thermal plasma torch 120 a to obtain first core-shell particles 3a, and introducing a second additive 2 b to the reactor 100 through athird feeder 110 c to be exposed to a second thermal plasma torch 120 btogether with the first core-shell particles 3 a to obtain core-shellparticles 3 b. The second core-shell particles 3 b have acore-multishell particle structure.

In the operation of adding the barium titanate-based base powder and theadditive to the reactor, the barium titanate-based base powder and theadditive may be separately added to the reactor through separatefeeders.

Alternatively, a plurality of the feeder 110, fewer than or more thanthat shown in the drawings, and a plurality of the thermal plasma torch120, fewer than or more than that shown in the drawings, may be disposedin the reactor 100.

In a method of producing the core-shell particles 3 according to anotherembodiment, first, the barium titanate-based base powder 1 is introducedinto the reactor 100 through the first feeder 110 a, and the firstadditive 2 a is introduced into the reactor 100 through the secondfeeder 110 b.

Another embodiment relates to a method of producing the core-shellparticles 3 according to the selective individual-type thermal plasmasynthesis method. In this case, the barium titanate-based base powder 1is introduced to the reactor 100 through the first feeder 110 a, and thefirst additive 2 a is added to the reactor 100 through the second feeder110 b. Thus, an embodiment of the present disclosure is characterized bythe barium titanate-based base powder 1 and the first additive 2 a whichare added to the reactor 100 through separate feeders.

Next, the barium titanate-based base powder and the first additive areexposed to the first thermal plasma torch 120 a to obtain the firstcore-shell particles 3 a.

By exposing the barium titanate-based base powder and the first additiveto the first thermal plasma torch 120 a, only the surface of the bariumtitanate-based base powder is activated in a rapid heating and coolingmanner.

The surface-activated barium titanate-based base powder and the firstadditives present in the surroundings react with each other to form thefirst core-shell particles 3 a.

For example, according to an embodiment, the barium titanate-based basepowder and the first additive are exposed to the first thermal plasmatorch 120 a, thereby obtaining the first core-shell particle 3 a thatincludes the core portion 1 including barium titanate (BaTiO₃) and thefirst shell portion 2 a including the first additive and formed on thesurface of the core portion 1.

Next, the second additive 2 b is introduced into the reactor 100 throughthe third feeder 110 c and exposed to the second thermal plasma torch120 b together with the first core-shell particles 3 a, to obtain thesecond core-shell particles 3 b.

For this reason, the second core-shell particles 3 b have acore-multishell particle structure.

For example, the second core-shell particles 3 b has a core-multishellparticle structure that includes the core portion 1 including bariumtitanate (BaTiO₃), the first shell portion 2 a having the first additiveand formed on the surface of the core portion 1, and the second shellportion 2 b including a second additive on the first shell portion 2 a.

In detail, as illustrated in FIGS. 2 and 3 , since the second core-shellparticles 3 b have a double shell structure, the second core-shellparticles 3 b may be referred to as core-double shell particles.

According to another embodiment, although not illustrated in FIGS. 2 and3 , additional additives in addition to the first and second additivesmay be further introduced into the reactor, and multiple shellsincluding additional additives may be further formed on the secondcore-shell particles 3 b.

For this reason, in the method of producing the core-shell particles 3according to another embodiment, the produced core-shell particles 3have a core-multishell particle structure, and the multishell may have adouble shell or more.

For example, the core-shell particles 3 may include a shell layer oftriple shell or more by further adding additional additives in additionto the first and second additives into the reactor as described aboveand exposing the additives to a further thermal plasma torch.

In the core-multishell particle structure, additives included inrespective shell layers of the multishell may be different materials.

For example, as described above, the first additive and the secondadditive may be different materials, and therefore, the additivesincluded in the first shell portion 2 a and the second shell portion 2 bmay be different materials.

In addition, in the core-multishell particle structure, the additivesincluded in respective shell layers of the multishell may have differentconcentrations.

For example, additives included in the first shell portion 2 a and thesecond shell portion 2 b may be different materials, and the additivesincluded in the first shell portion 2 a and the second shell portion 2 bmay have different measurement concentrations in respective shellportions.

In detail, although the first additive is mainly included in the firstshell portion 2 a, the first additive may also be detected in the shellportion of the second shell portion 2 b or more, and in this case, theconcentration of the first additive may be highest in the first shellportion 2 a.

In addition, although the second additive is mainly included in thesecond shell portion 2 b, the second additive may also be detected inthe shell portions of the first shell portion 2 a and the third shellportion or more, and in this case, the concentration of the secondadditive may be highest in the second shell portion 2 b.

In the case of a simple mixing method or heat treatment, which is arelated art method of producing core-shell particles, the uniformity ofthe particles is deteriorated, and since the designated additivematerial is added by random coating, there is a problem in thedispersion of the material, furthermore, in the product distribution forthe finished product.

However, the core-shell particles produced by the core-shell particleproduction method by the thermal plasma synthesis method according to anembodiment of the present disclosure are relatively less aggregated andeasier to synthesize ultra-fine particles than that in the related artmethods.

In addition, the thermal plasma treatment effect is applied at the sametime has the effect of sterilization and impurities removal.

In addition, when preparing the core-shell particles by thermal plasmasynthesis method as in an embodiment, the core-shell particles may beproduced only using the surface chemical reaction through the surfaceactivation without causing BT grain growth, in a fast chemical reactionrate and rapid heating and cooling manner.

In addition, low vacuum synthesis and raw material injection in theaxial direction enable mass production and continuous production.

In addition, the advantages in the case of the core-shell particleproduction method by the thermal plasma synthesis method according to anembodiment may be provided as follows.

Ultrafine particles having a narrow particle size distribution may beobtained depending on the production conditions. In addition, since theconcentration of substances in the gas phase is relatively low, theaggregation of generated particles is small.

In addition, the number of chemicals involved is small and thus easy tocontrol impurities, and the process is simpler and more widely used thanthe liquid phase method.

In addition, it is easy to control the synthetic atmosphere, andnonoxides such as nitrides, carbides, borides, and metals may beobtained in addition to oxides.

Volatile raw materials are easy to purify and high purity products maybe obtained. A starting material may be freely selected in solid state,liquid state and gaseous state. In this case, fast chemical reactionproperties of less than 10⁻² sec. may be provided. It is possible forthe short reaction time due to the rapid heating and cooling manner(>10⁶ K/s). In addition, velocity of the particles, degree of vacuum,and power of plasma are 100˜2,000 m/s, 10⁻²˜10⁻¹, and 10˜70 kW,repectively.

FIG. 4 is a perspective view schematically illustrating a multilayerceramic capacitor according to an embodiment.

FIG. 5 is a cross-sectional view taken along line I-I′ of FIG. 4 .

Referring to FIGS. 3 and 4 , a multilayer ceramic electronic componentaccording to another embodiment may include: a ceramic body 10 includinga dielectric layer 11, and internal electrode layers 21 and 22 disposedto face each other in the ceramic body 10 with the dielectric layer 11interposed therebetween. The dielectric layer 11 includes a core-shelldielectric grain 3 including a core portion 1 containing a bariumtitanate (BaTiO₃) and a shell portion 2 formed on the surface of thecore portion 1, as described above. In the case of the core-shelldielectric grain 3, the shell portion 2 has multiple layers, asdescribed above.

Hereinafter, a multilayer ceramic electronic component according to anembodiment will be described, and in detail, is described with amultilayer ceramic capacitor, but an embodiment thereof is not limitedthereto.

In the multilayer ceramic capacitor according to an embodiment, ‘lengthdirection’ is defined as ‘L’ direction of FIG. 4 , ‘width direction’ as‘W’ direction, and ‘thickness direction’ as ‘T’ direction. In this case,the ‘thickness direction’ may be used in the same concept as thedirection of stacking the dielectric layer, for example, the ‘stackingdirection’.

According to an embodiment, the raw material for forming the dielectriclayer 11 is not particularly limited as long as sufficient capacitancemay be obtained, and may be, for example, barium titanate (BaTiO₃)powder as described above.

In the core-multishell dielectric grain, the multishell may include ashell layer of a double shell or more as described above.

In addition, in the core-multishell dielectric grain, the additivesincluded in shell layers of the multishell structure may be differentmaterials.

In addition, in the core-multishell dielectric grain, the additiveincluded in the shell layers of the multishell may have differentconcentrations.

Other features are overlapped with the features of the method ofproducing the core-shell particles 3 according to the embodiment and theother embodiments described above, and thus will be omitted.

The material forming first and second internal electrodes 21 and 22 isnot particularly limited, and for example, a conductive paste formedusing one or more of, for example, silver (Ag), lead (Pb), platinum(Pt), nickel (Ni), and copper (Cu) may be used.

The multilayer ceramic capacitor according to an embodiment may furtherinclude a first external electrode 31 electrically connected to thefirst internal electrode 21 and a second external electrode 32electrically connected to the second internal electrode 22.

The first and second external electrodes 31 and 32 may be electricallyconnected to the first and second internal electrodes 21 and 22 to forma capacitance, and the second external electrode 32 may be connected toa potential different from that of the first external electrode 31.

The material of the first and second external electrodes 31 and 32 isnot particularly limited as long as the material may be electricallyconnected to the first and second internal electrodes 21 and 22 to formcapacitance. For example, the first and second external electrodes 31and 32 may include one or more selected from the group consisting ofcopper (Cu), nickel (Ni), silver (Ag), and silver-palladium (Ag—Pd).

As set forth above, according to embodiments, core-shell particles maybe implemented to obtain high performance and high reliabilitymultilayer ceramic capacitors by applying thermal plasma synthesis.

While this disclosure includes specific examples, it will be apparent toone of ordinary skill in the art that various changes in form anddetails may be made in these examples without departing from the spiritand scope of the claims and their equivalents. The examples describedherein are to be considered in a descriptive sense only, and not forpurposes of limitation. Descriptions of features or aspects in eachexample are to be considered as being applicable to similar features oraspects in other examples. Suitable results may be achieved if thedescribed techniques are performed to have a different order, and/or ifcomponents in a described system, architecture, device, or circuit arecombined in a different manner, and/or replaced or supplemented by othercomponents or their equivalents. Therefore, the scope of the disclosureis defined not by the detailed description, but by the claims and theirequivalents, and all variations within the scope of the claims and theirequivalents are to be construed as being included in the disclosure.

What is claimed is:
 1. A multilayer ceramic electronic componentcomprising: a ceramic body including a dielectric layer; and internalelectrode layers disposed to face each other with the dielectric layerinterposed therebetween in the ceramic body, wherein the dielectriclayer includes a core-shell dielectric grain including a core portionhaving barium titanate (BaTiO₃) and a shell portion disposed on asurface of the core portion, and the core-shell dielectric grain is acore-multishell dielectric grain in which the shell portion includes afirst shell portion and a second shell portion, wherein the first andsecond shell portions each include a first additive and a secondadditive, and wherein a concentration of the first additive in the firstshell portion is higher than in the second shell portion and aconcentration of the second additive in the second shell portion ishigher than in the first shell portion.
 2. The multilayer ceramicelectronic component of claim 1, wherein the first shell portion isdisposed on the surface of the core portion and the second shell portionis disposed on a surface of the first shell portion.
 3. The multilayerceramic electronic component of claim 1, wherein the first additiveincludes one or more of Dy, Y, V, Mg, Mn, Ba, Si, Al, Cr, or Ca.
 4. Themultilayer ceramic electronic component of claim 1, wherein the shellportion further includes at least a third shell portion.
 5. Themultilayer ceramic electronic component of claim 1, wherein the firstshell portion is disposed on the surface of the core portion and thesecond shell portion is disposed on a surface of the first shellportion, and wherein the shell portion further includes at least a thirdshell portion disposed on a surface of the second shell portion.
 6. Themultilayer ceramic electronic component of claim 1, wherein the shellportion further includes at least a third shell portion disposed on asurface of the second shell portion, wherein the third shell portionincludes the second additive, and the concentration of the secondadditive is highest in the second shell portion.